Keihin FCR Fitment M900

Darren69 · 01-06-2020, 12:55 PM

They're race carbs so not for really touring around on so what'd you expect? The throttle is heavier because you have more stuff to move now than you did with the girly CV's. Tuning potential has been unleashed however so now so the best thing you can do now with those carbs is get some 45/50mm headers and open cans get them set up on a dyno. The the biggest drawback with the standard setup is the standard 40mm header, will just kill it. Otherwise you won't get much advantage from them with a standard setup, just the bad stuff.

Luddite · 01-06-2020, 01:19 PM

Ahh! Carbs! Those were the days.

Darren's right about the headers but what sort of riding do you mostly do? Large diameter headers are great for top end power but the trade off is a loss in low end torque.

Smaller header diameters keep the gas speed up for more torque, while a larger diameter is better for higher RPM. Torque is related to the speed of the mixture passing through the engine, while horsepower is dependant on the volume of mixture that passes through. The quicker the mixture enters and leaves the engine, the more torque it'll make; the greater the volume of mixture that passes through, the more horsepower it'll develop.

So you'll need to decide which setup best suits your riding. I rarely trouble the top end of the rev range, so I won't be going large!

01-06-2020, 12:55 PM	#1
Darren69 Transmaniacon MOC Join Date: Sep 2013 Location: Sutton In Ashfield Bike: Multiple Monsters Posts: 6,025	They're race carbs so not for really touring around on so what'd you expect? The throttle is heavier because you have more stuff to move now than you did with the girly CV's. Tuning potential has been unleashed however so now so the best thing you can do now with those carbs is get some 45/50mm headers and open cans get them set up on a dyno. The the biggest drawback with the standard setup is the standard 40mm header, will just kill it. Otherwise you won't get much advantage from them with a standard setup, just the bad stuff. __________________ Roast Beef Monster! Termignoni and Bucci - Italian for pipe and slippers! S4 Fogarty, S4R 07T, 748, Series 1 Mirage

01-06-2020, 01:19 PM	#2
Luddite Registered User Join Date: Aug 2011 Location: Southampton Bike: M1100evo Posts: 2,465	Ahh! Carbs! Those were the days. Darren's right about the headers but what sort of riding do you mostly do? Large diameter headers are great for top end power but the trade off is a loss in low end torque. Smaller header diameters keep the gas speed up for more torque, while a larger diameter is better for higher RPM. Torque is related to the speed of the mixture passing through the engine, while horsepower is dependant on the volume of mixture that passes through. The quicker the mixture enters and leaves the engine, the more torque it'll make; the greater the volume of mixture that passes through, the more horsepower it'll develop. So you'll need to decide which setup best suits your riding. I rarely trouble the top end of the rev range, so I won't be going large!